Crystal structure orientation

At low coverages, most metallic adsorbates form ordered overlayers with a (1 x 1) surface structure on metal substrates. This implies that the substrate acts as a template and has a significant influence on the growth mode of the deposited material. This effect is usually called epitaxial growth. A more restricted definition of epitaxial growth would include only those examples where the substrate imposes its own crystal structure, orientation, and lattice parameter on the adsorbed overlayer. (This restricted definition is also called pseudomorphic growth.)... 

Savytskii, D. I. Crystal structure, orientation states and properties of rare earth gallates. Ph.D. thesis. 

Recent trends in x-ray diffraction are the increased use of electronic data collection and computer analysis, and in situ or dynamic experiments. These include experiments where the x-ray patterns are obtained while the sample is stretched, heated to its melting point, or aligned with an electric field. Synchrotron radiation is several orders of magnitude more intense than regular laboratory x-ray sources, and its use allows real-time study of deformation or fiber spinning, for example. More synchrotron sources usable for polymer science are currently being built, and although they are limited to national facilities, access should improve in the future. The increased power of computer data analysis permits whole pattern analysis where the crystal structure, orientation and crystallinity are simultaneously determined [10]. More detailed numerical analysis has led to interpretation of x-ray patterns in terms of three phases in semicrystalline polymers instead of the usual two. 

Friction and Wear, I.V. Kragelskii, Butterworths, 1965 available as an English translation. The Influence of Crystal Structure. Orientation and Solubihty on the Adhesion and Sliding of Various Metal Single Crystals in Vacuum (10 Torr), D.H. Buckley, ASTMSP—431,1968, pp. 248-271. 

Size and shape of spherulites Interior structure of spherulites Arrangement of lamellae Structure of lamellae Crystal structure, orientation... 

Stimuh in measurement may affect the data acquired. For example, in mechanical strength detection, the stress-strain profiles of a nanosolid may not be symmetric under tension and compression, and the flow stress is strain rate, loading mode, and materials compactness as well as size distribution dependent. However, one could not expect to cover the fluctuations of mechanical (strain rate, stress direction, loading mode, etc), thermal (self-heating during process and electron bombardment in TEM), crystal structure orientation, or grain-size... 

Method Molecular structure interactions Miscibility Surface and interphase Phase separation Crystal structure Orientation... 

The catalytic subunit then catalyzes the direct transfer of the 7-phosphate of ATP (visible as small beads at the end of ATP) to its peptide substrate. Catalysis takes place in the cleft between the two domains. Mutual orientation and position of these two lobes can be classified as either closed or open, for a review of the structures and function see e.g. [36]. The presented structure shows a closed conformation. Both the apoenzyme and the binary complex of the porcine C-subunit with di-iodinated inhibitor peptide represent the crystal structure in an open conformation [37] resulting from an overall rotation of the small lobe relative to the large lobe. 

Table 4.14 Spatial Orientation of Common Hybrid Bonds Figure 4.1 Crystal Lattice Types Table 4.15 Crystal Structure...

Fig. 3. Crystal structure and lattice distortion of the BaTiO unit ceU showiag the direction of spontaneous polarization, and resultant dielectric constant S vs temperature. The subscripts a and c relate to orientations parallel and perpendicular to the tetragonal axis, respectively. The Curie poiat, T, is also shown.

An example of research in the micromechanics of shock compression of solids is the study of rate-dependent plasticity and its relationship to crystal structure, crystal orientation, and the fundamental unit of plasticity, the dislocation. The majority of data on high-rate plastic flow in shock-compressed solids is in the form of ... 

The crystals, or grains, in a polycrystal fit together exactly but their crystal orientations differ (Fig. 10.4). Where they meet, at grain boundaries, the crystal structure is disturbed, but the atomic bonds across the boundary are numerous and strong enough that the boundaries do not usually weaken the material. 

As we have already seen, when an alloy contains more of the alloying element than the host metal can dissolve, it will split up into two phases. The two phases are "stuck" together by interphase boundaries which, again, have special properties of their own. We look first at two phases which have different chemical compositions but the same crystal structure (Fig. 2.5a). Provided they are oriented in the right way, the crystals can be made to match up at the boundary. Then, although there is a sharp change in... 

From a knowledge of the crystal structure it is possible to calculate selection rules for each orientation position and thus gain considerable insight into the vibrational motions of the crystal. The interpretation of such spectra, which show a lot of detail, goes well beyond characterization applications. ... 

Polymers can exist in a number of states. They may be amorphous resins, rubbers or fluids or they can be crystalline structures. TTie molecular and the crystal structures can be monoaxially or biaxially oriented. Heterogeneous blends of polymers in different states of aggregation enable materials to be produced with combinations of properties not shown by single polymers. 

Any orientation of molecules or crystal structures that may have been induced. 

Crystallography is a very broad science, stretching from crystal-structure determination to crystal physics (especially the systematic study and mathematical analysis of anisotropy), crystal chemistry and the geometrical study of phase transitions in the solid state, and stretching to the prediction of crystal structures from first principles this last is very active nowadays and is entirely dependent on recent advances in the electron theory of solids. There is also a flourishing field of applied crystallography, encompassing such skills as the determination of preferred orientations, alias textures, in polycrystalline assemblies. It would be fair to say that... 

Epitaxy. There is often a sharp orientation relationship between a singlecrystal substrate and a thin-film deposit, depending on the crystal structures and lattice parameters of the two substances. When such a relationship exists, the deposit is said to be in epitaxy with the substrate. The simplest relationship is parallel orientation, and this is common in semiconductor heterostructures, but more complex relationships are often encountered. 

Conversely, when A-alkyl tryptophan methyl esters were condensed with aldehydes, the trans diastereomers were observed as the major products." X-ray-crystal structures of 1,2,3-trisubstituted tetrahydro-P-carbolines revealed that the Cl substituent preferentially adopted a pseudo-axial position, forcing the C3 substituent into a pseudo-equatorial orientation to give the kinetically and thermodynamically preferred trans isomer." As the steric size of the Cl and N2 substituents increased, the selectivity for the trans isomer became greater. A-alkyl-L-tryptophan methyl ester 42 was condensed with various aliphatic aldehydes in the presence of trifluoroacetic acid to give predominantly the trans isomers. ... 

MW and MWD are very significant parameters in determining the end use performance of polymers. However, difficulty arises in ascertaining the structural properties relationship, especially for the crystalline polymers, due to the interdependent variables, i.e., crystallinity, orientation, crystal structure, processing conditions, etc., which are influenced by MW and MWD of the material. The presence of chain branches and their distribution in PE cause further complications in establishing this correlation. 

In most cases crystal densities differ from the densities of amorphous polymers. This leads to differences in refractive index, which in turn cause scatter of light at boundaries between amorphous and crystalline zones. Such materials are opaque except in certain instances where the crystal structure can be carefully oriented to prevent such scatter of light. 

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